Conventionally, in order to support driving of a driver of a vehicle, a device which controls an operation of a host vehicle automatically has been proposed. For example, Patent Literature 1 discloses a drive assisting device in which an inter-vehicle distance controller calculates a vehicle speed command value V* on the basis of an inter-vehicle distance L detected by an inter-vehicle distance sensor and a host vehicle speed VS detected by a vehicle speed sensor, a vehicle speed controller calculates a drive shaft torque command value TW* on the basis of the vehicle speed command value, and a drive shaft torque controller calculates a brake hydraulic pressure command value PB* and a throttle opening command value θ* on the basis of the drive shaft torque command value to thereby perform tracking control of a preceding vehicle and inter-vehicle distance control.
In the inter-vehicle distance controller, the inter-vehicle distance decontrol conditions are set so that inter-vehicle distance control is removed when the host vehicle speed Vs is equal to or lower than a decontrol vehicle speed VR and a preceding vehicle speed Vt is equal to or lower than the decontrol vehicle speed VR or a value lower than this or a relative vehicle speed ΔV is equal to or lower than “0”, Accordingly, in the device disclosed in Patent Literature 1, the inter-vehicle distance decontrol timing is set so that the frequency of driving resumption operations performed inconveniently by a driver is decreased.